The term fine pulp or fine fibres as used herein means fibres having a maximum diameter of less than 25 microns, a wall thickness of up to 2.5 microns and an aspect ratio of length to diameter of about 10. The term coarse pulp or coarse fibre as used herein means fibres having a diameter of at least 30 microns, a wall thickness of at least 13 microns and an aspect ratio of length to diameter of about 10.
Generally liner board is formed substantially solely from Kraft pulp which has been found necessary to provide the strength required. The liner is then laminated with a corrugated corrugating medium to form a single face and eventually with a second liner to form conventional corrugated board.
Western Red Cedar is used to make unbleached, bleached kraft or semibleached kraft pulp that finds use in a coating base stock, reinforcing fibre in newsprint or groundwood printing papers for making surgical gowns, etc.
When Western Red Cedar is mechanically pulped it has been found that it produces predominantly fine fibre pulp.
Mechanical pulping of Douglas Fir produces a relatively coarse fibre. The coarseness of the fibre can be varied depending on the degree of refining or secondary refining to which the fibres are subjected.